Claus Stadler <cstadler@xxxxxxxxxxxxxxxxxxxxxxxxx> writes: > Query optimizer glitch: "...WHERE TRUE" condition in union results in > bad query plan ... Yeah, this is because a nonempty WHERE clause defeats simplifying the UNION ALL into a simple "append relation" (cf is_safe_append_member()). The planner will eventually figure out that WHERE TRUE is a no-op, but that doesn't happen till later (and there are good reasons to do things in that order). Sooner or later I'd like to relax the restriction that appendrel members can't have extra WHERE clauses, but don't hold your breath waiting... regards, tom lane -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
